1. Field of the Invention
The invention relates to a stamp formed muffler with a siphon tube for evacuating moisture from chambers of the muffler.
2. Description of the Prior Art
The prior art exhaust system of a vehicle includes a muffler to attenuate the noise associated with the flowing exhaust gas. Exhaust gases produced by an engine include vaporized liquids. These vapors in the exhaust gas condense as the gas cools. Some such condensation occurs in the muffler while the vehicle is operating due to the cooling that occurs as the exhaust gas travels further distances from the engine. Additionally, vapor in the muffler condenses when the engine is turned off. Condensate in a muffler will flow to the gravitational low point of the muffler or to the gravitational low point of each chamber in the muffler. This condensate can accumulate at these low points and can lead to an accelerated corrosion or rusting of the outer shell or the baffles of the prior art muffler.
Corrosion caused by condensate in a muffler often is avoided by merely placing a hole through the outer shell approximately at the gravitational low point of each chamber. The holes are intended to permit gravitational outflow of condensate before damage to the muffler occurs. Holes generally work well. However many new car manufacturers prefer not to provide new equipment with a hole. Furthermore, there is a concern that moisture passing through the hole will wick into the space between the outer shell and the outer wrapper. This moisture may not drain well and can accelerate corrosion. There also is a concern that particulates in the exhaust gas will combine with the condensate to form a sludge that may block the hole and render the hole inoperative.
Some prior art mufflers have been provided with a porous material that is intended to absorb moisture vapor before the vapor can condense.
Other prior art mufflers have included siphon tubes. Siphon tubes have been employed by drilling or punching an aperture through a flow tube of a prior art muffler. A diametrically smaller siphon tube is then mitered and welded to the flow tube at the aperture and extends down into a chamber of the muffler generally near a gravitational low point. A pressure differential between the chamber and the flow tube draws moisture condensate from the gravitational low point through the small diameter siphon tube and into the flow tube of the prior art muffler.
An example of a muffler with a siphon tube is shown in published British Patent Appl. GB 2 134 979 A.
Siphon tubes can be effective for evacuating condensate from the chamber into which the siphon tube extends. However, most prior art mufflers include a plurality of chambers separated by baffles. These prior art mufflers have included apertures at the gravitational low point of the baffle to permit fluid to flow gravitationally downwardly into the chamber having the siphon tube. Although prior art mufflers of this type have worked well, it is often desirable to have adjacent chambers structurally and functionally separate from one another. Thus, apertures in baffles may compromise the performance of one or both chambers separated by the baffle.
Mufflers assembled from formed components have received considerable commercial interest in recent years. The typical prior art formed muffler includes a pair of plates formed with channels. The plates are secured in face-to-face relationship such that the channels define flow tubes for carrying exhaust gas. The prior art formed mufflers further include a pair of external shells that are formed to define chambers surrounding the tubes. Each external shell may include an inwardly formed crease that engages the adjacent plate and defines a baffle that effectively divides the external shell into a plurality of structurally and functionally separate chambers. Formed mufflers are shown for example, in reissued U.S. Pat. No. RE 33,370, U.S. Pat. No. 4,765,437 and U.S. Pat. No. 5,252,788 all of which are assigned to the assignee of the subject invention.
Formed mufflers are subject to the condensate accumulation that affects conventional mufflers. As a result there is a desire to prevent the accumulation of condensate in formed mufflers. Condensate can effectively be eliminated by apertures through the external shell at the gravitational low point of each chamber. However, as noted above, new car manufacturers often will not allow apertures through their mufflers. Additionally, stamp formed mufflers often are provided with laminated shells, and apertures create the potential for a wicking of moisture into the space between the laminated shells. The mitering and welding of tubes required to incorporate siphons into conventional mufflers is not well suited to the automated manufacturing and assembly techniques used for formed mufflers. Thus the prior art siphon tube technology would offset many of the manufacturing efficiencies provided with stamp formed mufflers. Additionally, the inwardly formed baffle creases of prior art stamp formed mufflers are not well suited to apertures that would permit a gravitational down flow of condensate into the gravitationally lowest chamber for evacuation by a siphon tube. Separate siphon tubes to each chamber of a stamp formed muffler would be costly and would further complicate manufacturing.
In view of the above, it is an object of the subject invention to provide a stamp formed muffler with a siphon tube for evacuating moisture from at least one chamber.
It is another object of the subject invention to provide a muffler with plural formed components and with a siphon for evacuating condensate from a plurality of chambers.